Copyright 2012 Scripps Media, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

NEW YORK (AP) - "Saturday Night Live" made a rare departure from its comedic opening to pay tribute to the children and adults killed at a Connecticut elementary school.

Not known for treating anything seriously or tenderly, the show made a fitting exception during the first moments of its show Saturday. Rather than the usual comedic sketch, a children's choir appeared on camera and angelically sang "Silent Night," with the touching refrain, "Sleep in heavenly peace."

Then the members of the New York City Children's Chorus shouted out the NBC show's time-honored introduction: "Live from New York, it's 'Saturday Night!'"

It was the night's sole reference to the tragedy and struck just the right tone.

Later, the chorus returned to join musical guest Paul McCartney in a rendition of his "Wonderful Christmas Time."

Appearing in a sketch in an unbilled cameo, actor Samuel L. Jackson made a distinctive contribution of his own.

Pretending to be miffed at getting interrupted as a guest on the mock talk show "What Up with That?" Jackson said what sounded very much like an F-bomb, followed by the term sometimes shortened to "B.S."

Playing the host of "What Up with That?" Kenan Thompson looked startled by Jackson's vulgarities but kept going.

"C'mon, Sam. That costs money!" he quipped, cracking up the studio audience.

Moments after the show ended, Jackson tried to explain in a Twitter posting.

"I only said FUH," he insisted, adding that Thompson was supposed to cut him off with his second eruption, but "blew it!!"

Jackson's tweet was accompanied by a photo of himself looking mortified.

Besides Jackson, some of the stars dropping by for this special Christmas "SNL" included Alec Baldwin, Tom Hanks, Kristen Wiig, Jimmy Fallon and Tina Fey. The guest host was Martin Short.